The Biometry Core provides biostatistical and data management support to all four projects, and to the other cores. These functions include: biostatistical analysis of final results, and intermediate results as necessary; data entry, storage, retrieval, and quality control; operational reporting on the progress of the projects; design of ancillary studies, and mid-course re-design of projects, when necessary, preparation of materials for internal and external monitoring committees. Additional responsibilities of the Biometry Core with respect to both projects and cores are: to remain current on pertinent analytic approaches in the biostatistical literature; to acquire and use specialized statistical software that is uniquely useful; to develop novel biostatistical methods in those cases where standard methods can be improved; and to work interactively with all investigators to ensure that the biostatistical analyses meet the scientific objectives of the projects and cores.